 @media all and (max-width: 400px) {
  
   #flash{ /*根据图片的大小来设置外层div的大小*/
     width: 100%;
     height: 150px;
     margin: 0 auto;
     position: relative; /*设置div定位，方便之后图片及圆点位置的设定*/
     border:1px solid black;
    }
   #flash img{
     width: 100%;
     height: 100%;
     position: absolute; /*设置所有图片重叠*/
     left: 0px;
     top: 0px;
     display: none; /*设置所有图片隐藏，通过改变第一个图片的行间样式来使第一个图片显示*/
    }
   #flash ul{
     width: 180px;
     height: 25px;
     border-radius: 20px;
     list-style:none;
     position: absolute;
     left: 25%;
     bottom:1px;
    }
   #flash ul li{
     width: 10px;
     height: 10px;
     margin-top:5px;
     background-color: #fff;
     border-radius: 50%;
     margin-left: 15px;
     float: left;
    }
   #flash ul .li_1{
     background-color: #f40; /*设置第一个圆点背景色为红色*/
    }
	/*左按钮*/
	/*
   #flash .span-r{
     width: 30px;
     height: 30px;
     border-radius: 50%;
     position: absolute;
     right: 2%;
     top: 45%;
     background-color: rgba(255,255,255,0.5);
    }
   #flash .span-r span{
     width: 100%;
     height:100%;
     color:rgba(0,0,0,0.5);
     font-size: xx-large;
     font-weight: 400;
     line-height: 30px;
     margin-left: 5px;
     cursor: pointer;
    }
	*/
	/*右按钮*/
	/*
   #flash .span-l{
     width: 30px;
     height:30px;
     border-radius: 50%;
     position: absolute;
     left: 2%;
     top: 45%;
     background-color: rgba(255,255,255,0.5);
    }
   #flash .span-l span{
     width: 100%;
     height:100%;
     color:rgba(0,0,0,0.5);
     font-size: xx-large;
     font-weight: 400;
     line-height: 30px;
     margin-left: 2px;
     cursor: pointer;
   }
   */
 }